U.S. patent application number 11/061124 was filed with the patent office on 2005-10-06 for plate heat and mass exchanger with edge extension.
Invention is credited to Gillan, Alan D., Gillan, Leland E., Gillan, Rick J., Heaton, Timothy L., Maisotsenko, Valeriy.
Application Number | 20050217303 11/061124 |
Document ID | / |
Family ID | 34886176 |
Filed Date | 2005-10-06 |
United States Patent
Application |
20050217303 |
Kind Code |
A1 |
Gillan, Leland E. ; et
al. |
October 6, 2005 |
Plate heat and mass exchanger with edge extension
Abstract
Heat exchanger plates for indirect evaporative coolers, of the
type having a dry side having low permeability to an evaporative
liquid and formed to allow a product fluid to flow over a heat
transfer area of its surface, a wet side designed to have its
surface wet by an evaporative liquid, and formed to allow a working
gas to flow over its surface to evaporate the evaporative liquid,
further include edge extensions formed beyond the heat exchange
area of the plates to facilitate removal of excess evaporative
liquid. The edge extensions may slant or curve away from the wet
side of the plates to assist in liquid removal. The plates may be
used in a variety of configurations.
Inventors: |
Gillan, Leland E.; (Denver,
CO) ; Maisotsenko, Valeriy; (Aurora, CO) ;
Heaton, Timothy L.; (Arvada, CO) ; Gillan, Alan
D.; (Denver, CO) ; Gillan, Rick J.; (Golden,
CO) |
Correspondence
Address: |
JENNIFER L. BALES
MOUNTAIN VIEW PLAZA
1520 EUCLID CIRCLE
LAFAYETTE
CO
80026-1250
US
|
Family ID: |
34886176 |
Appl. No.: |
11/061124 |
Filed: |
February 18, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60545672 |
Feb 18, 2004 |
|
|
|
Current U.S.
Class: |
62/314 ;
62/304 |
Current CPC
Class: |
F24F 5/0035 20130101;
F24F 13/222 20130101; F24F 1/0007 20130101; F24F 1/0059 20130101;
Y02B 30/54 20130101; F28D 5/02 20130101 |
Class at
Publication: |
062/314 ;
062/304 |
International
Class: |
F28C 001/00; F28D
005/00 |
Claims
What is claimed is:
1. A heat exchanger plate for use in an indirect evaporative
cooling system, the plate comprising: a dry side having low
permeability to an evaporative liquid and formed to allow a product
fluid to flow over a heat transfer area of its surface; a wet side
designed to have its surface wet by an evaporative liquid, and
formed to allow a working gas to flow over its surface to evaporate
the evaporative liquid; and an edge extension formed at the edge of
the plate, beyond the heat transfer area, for causing excess
evaporative liquid to drip off the plate.
2. The plate of claim 1, wherein the edge extension slopes away
from the wet side.
3. The plate of claim 1 formed as an integral piece of a single
material.
4. The plate of claim 3 wherein the material is aluminum.
5. The plate of claim 4, wherein the wet side is textured to form a
wicking surface.
6. The plate of claim 3, further comprising a wicking material
attached to the wet side of the plate.
7. The plate of claim 1, wherein the wet side includes a wicking
surface.
8. The plate of claim 1, wherein the wet side includes channel
guides to channel the working gas.
9. The plate of claim 8, wherein the working gas flows in a
direction other than toward the edge extension, and wherein the
evaporative liquid flows under the channel guides to reach the edge
extension.
10. An indirect evaporative cooler comprising: a plurality of
generally parallel, spaced apart plates wherein each plate has a
dry side having low permeability to an evaporative liquid and
formed to allow a product fluid to flow over a heat transfer area
of its surface; a wet side designed to have its surface wet by an
evaporative liquid, and formed to allow a working gas to flow over
its surface to evaporate the evaporative liquid; and an edge
extension formed at the edge of the plate, beyond the heat transfer
area, for causing excess evaporative liquid to drip off the plate;
wherein the edge extensions extend beyond the edge of the heat
transfer areas of the plates for a distance at least the distance
between the plates.
11. The indirect evaporative cooler of claim 10 wherein the plates
are oriented generally vertically and the edge extensions are
located at the bottoms of the plates.
12. The indirect evaporative cooler of claim 10 wherein the plates
are oriented generally horizontally.
13. The indirect evaporative cooler of claim 10 wherein the plates
are slanted downward in each direction from a center axis.
14. The indirect evaporative cooler of claim 13, further comprising
a trough located at the center axis, the trough containing the
evaporative fluid.
15. The indirect evaporative cooler of claim 14, wherein the plates
include a wicking material on their wet sides.
16. The indirect evaporative cooler of claim 10, wherein the
working gas flows in a direction other than toward the edge
extensions, and wherein the evaporative liquid flows under the
channel guides to reach the edge extensions.
17. The indirect evaporative cooler of claim 10, wherein the plates
include a wicking material on their wet sides.
Description
[0001] U.S. Pat. No. 6,581,402, issued Jun. 24, 2003 is
incorporated herein by reference. U.S. Pat. No. 6,705,096, issued
Mar. 16, 2004 is incorporated herein by reference. This application
claims the benefit of U.S. Provisional Patent Application No.
60/545,672, filed Feb. 18, 2004.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to plate heat and mass
exchangers for indirect evaporative coolers. In particular, the
present invention relates to such plates having edge extensions for
enhanced fluid removal.
[0004] 2. Discussion of the Background Art
[0005] Indirect evaporative cooling is a method of cooling a fluid
stream; usually air, by evaporating a cooling liquid, usually
water, into a second air stream while transferring heat from the
first air stream to the second. The method has certain inherent
advantages compared to conventional air conditioning: low
electricity requirements, relatively high reliability, and the
ability to do away with the need for refrigerants such as R-134 and
all the disadvantages they entail.
[0006] U.S. Pat. No. 6,581,402 shows a number of embodiments for
indirect evaporative cooling using plate apparatus. FIG. 1 (Prior
art) shows a perspective and schematic representation of two plates
showing the wet side channels formed by the wet sides of a first
and a second plate opposing each other, with their passages
oriented in the same general area and illustrating the working gas
entering on the dry side, passing through the passages and into the
wet side channels. The product fluid is separated from the working
gas as they pass along the dry side of the first and second plates.
Additional plates form a stack, and adjacent plates have their dry
sides facing each other. Thus, the stack of plates would have every
odd plate oriented with its dry side facing the same direction and
opposite of all even plates.
[0007] The invention of U.S. Pat. No. 6.581,402 provides an
indirect evaporative cooler having cross flowing wet and dry
channels on opposite sides of a plurality of heat exchange plates
which allow heat transfer through the plates. The plates include
edge extensions to facilitate the removal of water (or similar
evaporative fluid) and dissolved minerals from the plates.
[0008] For purposes of both U.S. Pat. No. 6.581,402 and the present
application, we wish to define certain terms:
[0009] 1. Heat transfer surface or heat exchange surface has many
configurations. All are encompassed within the subject of this
disclosed invention with appropriate adjustment to the wetting and
flows as are well known in the industry. For illustration we make
use of a plate configuration.
[0010] 2. Wet side or wet portion of the heat exchange surface
means that portion having evaporative liquid on or in its surface,
thus enabling evaporative cooling of the surface and the absorption
of latent heat from the surface.
[0011] 3. Dry side or dry portion of the heat exchanger means that
portion of the heat exchanger surface where there is little or no
evaporation into the adjacent gas or fluid. Thus, there is no
transfer of vapor and latent heat into adjacent gases. In fact, the
surface may be wet but not with evaporative fluid or wet by
condensation, but no evaporation exists.
[0012] 4. Working stream or working gas stream is the gas flow that
flows along the heat exchange surface on the dry side, passes
through the passages in the surface to the wet side and picks up
vapor and by evaporation, taking latent heat from the heat exchange
surface and transporting it out into the exhaust. In some
embodiments, the working stream may be disposed of as waste and in
others it may be used for special purposes, such as adding humidity
or scavenging heat.
[0013] 5. Product stream or product fluid stream is the fluid (gas,
liquid or mixture) flow that passes along the heat exchange surface
on the dry side and is cooled by the absorption of heat by the
working gas stream on the wet side absorbing latent heat by the
evaporation in the wet area.
[0014] The plate also has passageways or perforations or similar
transfer means between the dry side of the plate and the wet side
in defined areas providing flow from the dry working channels to
the working wet channels in which direct evaporative cooling takes
place.
[0015] The method of the invention makes use of the separation of a
working gas flow (that is used to evaporate liquid in the wet
channels and thus to cool the wet surface of the heat exchanger
plate) from the product fluid flow, flowing through dry product
channels and dry working channels respectively on the same side of
the heat exchange plate. Both give up heat to the heat exchange
plate that on its obverse surface is being cooled by evaporation in
the working wet channels.
[0016] The working gas flow first enters the dry working channel
and then through perforations, pores or other suitable means of
transfer across the barrier of the plate to the wet side and thence
into the wet working channels where evaporation of liquid on the
wet channel surface, cools this plate.
[0017] The dry product channels are on the dry side of this plate.
The plate is of a thin material to allow easy heat transfer across
the plate and thus to readily allow heat to transfer from the dry
product channel to the wet working channel. This is one basic unit
or element of the invention illustrating the method of the
separation of working gas flows to indirectly cool the separate
product fluid by evaporative cooling.
[0018] Many evaporative cooling embodiments include a wicking
material for distributing the water or other evaporative liquid
over the plate wet side. See, for example, FIG. 7 of U.S. Pat. No.
6,581,402, wherein a wicking material 7 distributes the evaporative
liquid along wet side channels 5. Plates 6 form a "V-shape" in the
embodiment of FIG. 7. Water also evaporates better from a wicking
surface that from a water surface, as the wick material breaks down
the surface tension of the water.
[0019] Wicking up a vertical surface will insure no excess water on
the plate surface but also limits the height of the plate that can
be used. Wicking water down a surface aided by gravity may be good
from a wetting perspective if the amount of water does not exceed
what the wick can transport. Wicking in a more horizontal direction
can allow a vertical reservoir wetting system such as shown in U.S.
Pat. No. 6,705,096. There are some plate heat and mass exchanger
applications that require a more innovative geometry that
corresponds to a more complicated thermodynamic design that again
require a more horizontal application such as U.S. Pat. No.
6,581,402. In all cases creating a means to insure that the wick
will not be over run by water is desired.
[0020] The indirect evaporative cooler of U.S. Pat. No. 6,581,402
works well. But a disadvantage inherent in the design has been
found in use. Sloping the plates to allow gravity to help pull
water through the wick helped to remove excess liquid and washing
minerals off the plates. However, the closely spaced heat exchanger
plates, with wicking surfaces facing each other, allowed water to
build up in the channels. This buildup was caused by the surface
tension of the water adhering the edge of the plates. For example,
given two horizontal plates in parallel, a drip from the top plate
would hang down and adhere to a drip on the lower at the plate
edges. Water would then back up from the edges of the plates on the
wick surfaces giving two detrimental effects. First the surface
water significantly reduced the heat transfer rate and thus the
cooling of the fluid on the opposite side of the plate. Second,
this over wetting between the plates caused an uneven airflow
distribution across the wet plates and therefore uneven cooling of
the fluid to be cooled on the opposite side of the plates.
[0021] As water in the wet channels is evaporated any dissolved
minerals that were in the water are left behind. Even if not all of
the water is evaporated away, when the minerals in the water become
too concentrated they deposit on any surface they come into contact
with. Such deposited minerals present a long-term problem, as they
build up and eventually impede the flow of water, particularly in
the wick material. Portions of the plate are no longer thoroughly
wetted, and heat exchange efficiency drops.
[0022] Therefore, a need remains in the art for apparatus and
methods for drawing excess liquid and minerals away from the heat
exchanging portion of the plate, and removing them from the
plate.
SUMMARY OF THE INVENTION
[0023] It is an object of the present invention to provide
apparatus and methods for drawing excess liquid and minerals away
from the heat exchanging portion of the plate, and removing them
from the plate.
[0024] Edge extensions are added to the plates of indirect
evaporative coolers to allow excess evaporative liquid to migrate
to the edges of the plates and drip off, taking dissolved minerals
with it. Better evaporation and heat transfer can also be
accomplished.
BRIEF DESCRIPTION OF THE DRAWINGS
[0025] FIG. 2a is a perspective and schematic representation of a
first embodiment of the present invention, having slanted edge
extensions. FIG. 2b is a side view of embodiment of FIG. 2a.
[0026] FIG. 3 is a side view of a second embodiment of the present
invention, having straight edge extensions.
[0027] FIG. 4 is a perspective and schematic representation of a
third embodiment of the present invention, utilizing a counter flow
design and having slanted edge extensions.
[0028] FIG. 5 is a perspective and schematic representation of a
fourth embodiment of the present invention, with the plates in a
vertical orientation having straight edge extensions.
[0029] FIG. 6 is a perspective and schematic representation of a
fifth embodiment of the present invention, with an integral design
and having slanted edge extensions.
[0030] FIG. 7 is a end cut-away view of a sixth embodiment of the
present invention, in which the plates slant downward from a center
axis and having a trough system for wetting the plates.
DETAILED DESCRIPTION OF THE INVENTION
[0031] FIGS. 2a-6 show various embodiments of edge extensions added
to heat transfer plates in indirect evaporative coolers. While
several embodiments are shown, it will be apparent to those skilled
in the art that the edge extensions can be added to many other
indirect evaporative cooler plates. U.S. Pat. Nos. 6,581,402 and
6,705,096, incorporated herein by reference, show a variety of
plate configurations, and others are known as well. In each case,
the edge extensions are added to the edges of the plates, beyond
the heat exchange portion of the plates, and facilitate removal of
excess evaporative liquid from the wet sides of the plates. While
the term "beyond the heat exchange of the plates" is used to
indicate that the edge extensions are added to the sides or ends of
the plates, this does not imply that no heat exchange can occur
there. The following table lists reference numbers used in this
patent:
1 1 dry side product fluid (e.g. air) 2 working gas (e.g. air) 3
dry side product channels (perforation embodiments) 4 dry side
working channels 5 wet side channels 6 plates 7 channel guides 8
wick material 9 dry sides of plates 10 wet sides of plates 11
perforations 20 edge extensions 21 length of edge extensions 22
evaporative fluid (e.g. water) 23 trough for wetting plates 24
Non-permeable layer 25 Wicking layer
[0032] FIG. 2 a is a perspective and schematic representation of a
first embodiment of the present invention, having slanted edge
extensions 20. FIG. 2b is a side view of embodiment of FIG. 2a. The
plates 6 in FIGS. 1a and 1b are shown as horizontal, but they may
also be tilted (see for example FIG. 7 of U.S. Pat. No.
6,581,402.
[0033] The embodiment of FIGS. 1a and 1b is a transverse-flow
design somewhat similar to that of FIG. 1 (Prior Art). Each plate
has a dry side 9, and the dry sides face each other. Dry sides 9
include dry side channels 4, through which product fluid 1 flows.
Wet sides 10 have wet side channels 5 through which working gas 2
flows. The wet side channels 5 are generally transverse to the dry
side channels 4.
[0034] Wet side channels 5 are wetted by an evaporative liquid 22,
via wicking, spraying or a similar method. The specific embodiment
shown in FIGS. 2a and 2b does not show working channels for passing
a working fluid through the plates from the dry side to the wet
sides, as is shown in FIG. 1(Prior Art), but those could be
included in the FIG. 2 embodiment. FIG. 2b shows the excess
evaporative fluid 22 flowing out of wet side channel 5 and dripping
off edge extensions 20 of plates 6. The slanted edge extensions,
which extend a distance 21 off the end of plates 6, facilitate this
fluid removal by opening up the space beyond the heat transfer
portion of wet sides 10.
[0035] In a particular preferred embodiment of an indirect
evaporative cooling system (described here by way of an example),
80 plates are stacked in a 10 inch high stack. The dimensions of
the plates are 20 inches by 18 inches. The plate material is
polyethelene coating on cellulose fiber paper (the paper acts as a
wicking material). The spacing between the plates is 0.125
inches.
[0036] In practice, edge extension lengths 21 of 1/2 inch and 1
inch work very well in causing excess evaporative liquid 22 to
drain. With plate spacing of around 0.125 inches, edge extensions
of substantially under 1/4 inch do not work as well ({fraction
(1/16)} inch does not work at all with this plate spacing).
However, with tighter plate spacings, edge extensions of a small as
1/8 inch are expected to accomplish the goal of efficiently
removing excess evaporative liquid. Edge extensions substantially
longer than plate spacing work best.
[0037] FIG. 3 is a side view of a second embodiment of the present
invention, very similar to that of FIGS. 2a and 2b, but having
straight edge extensions. Much of the discussion related to FIGS.
2a and 2b is relevant to this embodiment as well.
[0038] Edge extension 20 in the embodiment of FIG. 3 extend
straight out, rather than curving away from wet sides 10. This
design is easier to fabricate than the design of FIGS. 2a and 2b,
and does remove excess evaporative fluid better than conventional
plates without edge extensions.
[0039] FIG. 4 is a perspective and schematic representation of a
third embodiment of the present invention, utilizing a counter-flow
design and having slanted edge extensions 20. Rather than having
wet side channels 5 and dry side channels 4 transverse to each
other, they are generally parallel, but flow in opposite
directions. The edge extension is generally transverse to the wet
side channel guides so that the working gas flows in a direction
other than toward the edge extension (perpendicular in the
embodiment of FIG. 4). Evaporative liquid 22 still coats wet side
channels 5 through wick material 8, and migrates via wicking under
channel guides 7, so that excess liquid travels to edge extensions
20 and drips off.
[0040] Migration of evaporative liquid 22 under channel guides 8 is
accomplished as follows. Plates 6 are formed of a wicking material
25 backed by a material 24 that is impermeable to the evaporative
liquid 22. For example, plates 6 might be formed of polyethelene
coating 24 on cellulose fiber paper 25. Paper 25 acts as a wicking
material, wicking liquid 22 under channel guides 7 and out to edge
extensions 22, where liquid 22 drips off of the plates.
[0041] FIG. 5 is a perspective and schematic representation of a
fourth embodiment of the present invention, with the plates 6 in a
vertical orientation, and having straight edge extensions 20
Working gas flow 2 is upward in wet side channels 5 and product
fluid flow 1 is sideways along dry side channels 4. Evaporative
liquid flows down channels 5 from the top and drips off edge
extensions 20 at the bottom.
[0042] FIG. 6 is a perspective and schematic representation of a
fifth embodiment of the present invention, with an integral design
and having an integral form of slanted edge extensions 20. The
embodiment of FIG. 6 is preferably formed of a solid block of a
single material, such as extruded aluminum. This design is
advantageous when the plates will be under some stress, such as
when the indirect evaporative cooler is pressurized.
[0043] In some applications of the invention the plates 6 and
spacers 7 may be formed out of rigid materials such as aluminum. In
such cases the plates 6 and plate spacers 7 may be extruded in one
piece such as shown in FIG. 6. The edge extensions 20 of plates 6
are preferably tapered to have a larger opening at the edges, to
facilitate excess liquid 22 dripping off. The evaporative (wet)
side of the plates 10 requires structure to have the evaporate 22
distribute over its surface. Distributing the evaporate can be
accomplished with either flocking material or by etching the
surface of a material such as aluminum creating a wick surface.
[0044] Hydrophilic surfaces, such as described in U.S. Pat. No.
6,568,465 to Meissner et al can act as wicking surfaces.
[0045] FIG. 7 is an end cut-away view of a sixth embodiment of the
present invention, in which plates 6 slant downward from a center
axis. A trough 23 contains evaporative liquid 22 for wetting the
plates. Generally a wicking material 25 (see FIG. 4 for an example)
draws liquid 22 from trough 23 along wet side channels 5. As liquid
22 reaches the outer ends of plates 6, it is drawn off the plates
by edge extensions 20, here shown as slanted edge extensions
similar to those shown in FIGS. 2a and 2b .
[0046] Those skilled in the art of indirect evaporative cooling
systems will recognize various changes and modifications which can
be made to the exemplary embodiments shown and described above,
which are still within the spirit and scope of the invention. In
all cases, edge extensions on the heat exchanger plates extend past
the heat transfer area of the plates and assist the evaporative
fluid in draingin off the plates.
* * * * *